Pfizer has bagged US approval for Besponsa – its treatment for adults with relapsed or refractory B-cell precursor acute lymphoblastic leukemia (ALL) – two months after it got the go-ahead in Europe.
Besponsa (inotuzumab ozogamicin), which had breakthrough status, was approved after a priority review by the FDA as this type of leukaemia is aggressive, has a very poor prognosis in adults, and limited treatment options.
The antibody drug conjugate (ADC) targets CD22-positive cells and delivers the toxic compound calicheamicin into the interior of cells, so is designed to kill tumour cells with minimal effects on healthy tissue. It is the first CD22-targeted ADC to be approved for marketing in the US, according to Pfizer.
The approval is based on the results of the phase III INO-VATE ALL trial involving 326 patients with relapsed or refractory ALL, which showed that inotuzumab outperformed current standards of care. The rate of complete remission was significantly higher in the inotuzumab ozogamicin group than in a group treated with standard chemotherapy – 81% versus 29%, respectively.
“For adult patients with B-cell ALL whose cancer has not responded to initial treatment or has returned after treatment, life expectancy is typically low,” commented Richard Pazdur, head of the FDA’s Office of Hematology and Oncology Products. In fact most patients with relapsed ALL are referred for investigational therapies.
“These patients have few treatments available and today’s approval provides a new, targeted treatment option.”
Mikael Dolsten – Pfizer‘s president of worldwide R&D – recently described the drug as “a highly differentiated drug for patients at great need”, noting that the company estimates that there are approximately 2,250 new cases of ALL diagnosed in adults in the US every year.
“As a result, this represents a meaningful new option for patients and a meaningful opportunity for us,” he added. Pfizer is pricing the drug at just under $170,000 per typical treatment course, before any discounts or rebates, and while some analysts have predicted relatively modest sales in the $250m region others have suggested it could approach blockbuster status with sales of $1bn or more.
Patients with relapsed and refractory B-cell ALL could get another treatment option in the coming months if Novartis claims approval for its CAR-T immunotherapy tisagenlecleucel-T, which recently cleared an FDA advisory committee and has also been filed in the EU.
Besponsa has been approved with a boxed warning for hepatotoxicity and an increased risk of post-hematopoietic stem cell transplantation non-relapse mortality. Pfizer was also developing the ADC for relapsed or refractory aggressive non-Hodgkin’s lymphoma and diffuse large B cell lymphoma (DLBCL) but has discontinued those programmes.